I. Technical Field
This invention is concerned with wireless telecommunications, and is particularly concerned with resource allocation for an uplink transmission in a wireless packet data telecommunications system.
II. Related Art and Other Considerations
In a typical wireless or cellular radio system, wireless user equipment units (UEs) communicate via a radio access network (RAN) to one or more core networks. The user equipment units (UEs) can be mobile stations such as mobile telephones (“cellular” telephones) and laptops with mobile termination, and thus can be, for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data with radio access network. Alternatively, the wireless user equipment units can be fixed wireless devices, e.g., fixed cellular devices/terminals which are part of a wireless local loop or the like.
The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by a unique identity, which is broadcast in the cell. The base stations communicate over the air interface (e.g., radio frequencies) with the user equipment units (UE) within range of the base stations. In the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a radio network controller (RNC). The radio network controller, also sometimes termed a base station controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks. The core network has service domains, with the radio access network having an interface to each of the service domains. For example, the core network typically has a circuit switched domain and a packet switched domain. Accordingly, the radio access network is typically configured to support or accommodate both circuit switched and packet switched connections.
One example of a radio access network is the Universal Mobile Telecommunications (UMTS) Terrestrial Radio Access Network (UTRAN). The UMTS is a third generation system which in some respects builds upon the radio access technology known as Global System for Mobile communications (GSM) developed in Europe. UTRAN is essentially a radio access network providing wideband code division multiple access (WCDMA) to user equipment units (UEs). The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM-based radio access network technologies. Other types of telecommunications systems which encompass radio access networks include the following: Advance Mobile Phone Service (AMPS) system; the Narrowband AMPS system (NAMPS); the Total Access Communications System (TACS); the Personal Digital Cellular (PDS) system; the United States Digital Cellular (USDC) system; and the code division multiple access (CDMA) system described in EIA/TIA IS-95.
There have been many proposals to use wireless packet data systems such as HSPA, CDMA-1x-EV-DO, and WiMAX for voice telephony using Voice over Internet Protocol (VoIP) mechanisms. The voice signal is encoded into packets that are then transmitted over a packet data channel. Similar principles can be applied to the use of the packet data system for other real-time applications such as video telephony etc. For many such real time applications, the encoded packets occur at a regular frequency, and it makes sense to allocate resources for the transmission of such packets on a regular basis.
In general, packet data systems allocate transmission on an as needed basis, e.g., if a wireless station has data to send, it makes a request and is allocated resources. The resource allocation has to be signaled to the wireless station. This signaling uses bandwidth that otherwise could be used to transmit actual user data to other users. For an application that is expected to transmit packets on a regular basis, one method of operating a packet data system involves the use of a persistent resource allocation, e.g., resources are allocated on a regular basis to the wireless station for the transmission of these regular packets. The persistent allocation can be signaled to the wireless station on a long-term basis, rather than signaling an allocation for every packet, thereby saving signaling bandwidth.
Many wireless telecommunications systems employ some type of feedback mechanism to provide a notification whether a transmission was properly received or not. Typically such systems provide a positive acknowledgement of receipt (ACK) or a negative notification (NACK) in the event of non-receipt or suspected faulty receipt of transmission contents. To assess transmission contents, many receivers have content checkers which can operate upon features of the transmission contents, such features including appended check or correction characters. When such a checker provides a negative notification (NACK) to a transmitter, the transmitter may be provided with another opportunity to transmit the non-received or supposed erroneous contents.
Most packet data systems also use Hybrid Automatic Repeat Request (Hybrid ARQ, or “HARQ”) as a means to improve transmission efficiency. In Hybrid ARQ, a retransmitted packet is combined with the earlier transmitted packet and then decoded to produce a more reliable estimate of the transmitted packet than with one transmitted packet alone. With hybrid ARQ usage, the operating point (in terms of the carrier to interference ratio [C/I], the modulation and coding scheme etc.) can be chosen more aggressively (than without hybrid ARQ) to permit more retransmissions, while still maintaining a comparable quality of service while simultaneously achieving a higher throughput for the packet data system. However, it is clear that the use of retransmissions requires transmission bandwidth over and above what is required to transmit the packets as determined by the application.
A problem with the existing on-demand allocation method is the high signaling bandwidth needed for conveying information on the allocation to the terminal. The persistent allocation would work reasonably well in the absence of ARQ. However, with ARQ, the need for a retransmission changes with channel conditions and interference levels, and is unpredictable. Thus, the persistent allocation scheme will have to over-allocate resources to account for the additional resources needed for ARQ, or will have to supplement the persistent allocation with an on-demand allocation method. This entails similar problems as to signaling overhead as mentioned earlier.